This invention relates generally to a trenching and edging devices for digging trenches and for edging the soil for beds for flowers, shrubbery, mulch, etc. 
Small trenching machines find application in those circumstances where it is necessary to dig a relatively narrow trench. This could be the case where cable TV is being buried to provide service to a residence or business, or could be when it is necessary to run a gas line, waterline, or other utility to a home or office. Further uses of such a trench could be for running irrigation line or what is known as radio or “invisible” fencing used to keep pets within a confined area, the pet then wearing a cooperating collar which is activated to shock the animal in the event the animal comes too close to the buried line. 
Edging machines find use with landscapers and homeowners for defining a bed used for ornamental plantings, shrubbery, flowers,  mulch, or the like and serve to form the defined edge of a bed to be created by cutting the soil to a depth, typically several inches, and then lifting the soil and moving it outwardly to form a mounded periphery for the bed. Generally, it is desirable that the turf adjacent the bed have a distinct, clean break between it and the bed. This provides for a clean definition of the bed which is desired for aesthetic and maintenance purposes. 
In certain instances, use of a trencher or edging machine is complicated by the fact that such machines are large, bulky, and heavy. They may require the use of a truck or trailer for transport, and may require two or more persons in order to load or unload the machine. Once in operation, because of the size and weight of such machines, they may pose a problem for use by someone of lesser strength or stature. Further, by requiring a larger vehicle, such as a truck, or sport utility vehicle, or alternately, use of a trailer, for transport, such machines may find only limited use, and their full potential for use may not be recognized. 
Trenching machines and edging machines are known. For example, U.S. Pat. No. 4,939,854, issued to Boren, discloses a trencher having a digging depth adjustment configuration including a rotatable handle in order to accomplish such depth adjustment. U.S. Pat. No. 4,002,205, issued to Falk, and U.S. Pat. No. 5,226,248, issued to Pollard, both disclose bed edge forming machines for forming the edge of a bed. 
U.S. Pat. No. 5,320,451, issued to Garvey, et al, discloses a tiller having a cable-laying attachment and also a provision for  carrying a spool-of cable, and a feed tube through which the cable is inserted into a trench. U.S. Pat. No. 5,009,270, issued to Vangsgard, discloses a sod-cutting machine having an adjustable depth adjustment, and U.S. Pat. No. 4,958,457, issued to Doskocil, and 4,979,573, issued to Williamson, both disclose devices using caster wheels for steering. The Doskocil device includes rear-mounted casters. 
In view of the foregoing known devices, there still exists a need for a combination trenching and edging device which is designed to facilitate movement and steering of the device and which also can be used to dig at varying depths. 
A need also exists for a trenching machine and an edging machine which are relatively lightweight and of relatively compact size to allow their easy transport and use by a wide variety of users. Ideally, such machines would be small enough to fit into the trunk of an ordinary sedan and light enough to be loaded and unloaded by one or two persons of average strength. 